First: I took the lower leg from some old jeans, to cut the main skirt from. I measured the waist of the doll, then cut a length 1 and half times as long as the measurement. The jeans I used weren't long enough so I just sewed 2 pieces together. The length of the skirt is the measurement from the Doll's waist to the knee.
Second: I cut a strip of fabric 3 inches wide, and 3 times as long as the waist measurement to make a ruffle. Fold the width of ruffle in half, and baste together. Gather up the ruffle and sew onto the skirt.
Third: I made a casing for the elastic, threaded the elastic through and TA-DA! All done!